Linnaeus saw Roman battle trophies in the humble garden nasturtium
When Carl Linnaeus named the nasturtium genus Tropaeolum, its round leaves reminded him of shields and its red flowers of helmets, like the trophy poles Romans hung with captured armour. The common name means nose-twister, from a peppery oil much like watercress, and every part of the garden species can be eaten.
Tropaeolum holds roughly 80 annual and perennial species native to South and Central America and is now the only genus in its family. A molecular study in 2000 showed that two small genera split off for having winged fruit or no spurs actually sat inside Tropaeolum, so they were folded back in. The flowers are bright and lopsided, with five petals and a funnel-shaped nectar spur formed from a modified sepal; the shield-shaped leaves are attached to their stalks at the centre, and many stalks twine around supports.
The familiar garden nasturtium is a hybrid of several species, usually grown as a half-hardy annual in cream, yellow, orange or red. It does best in poor, dry soil; rich ground yields leaves at the expense of flowers. Relatives include the Canary creeper, originally from Peru, the blue nasturtium of Chile, and the flame flower, which famously thrives in cool, damp Scotland. The wreath nasturtium's tubers can sit 60 centimetres deep, letting it survive at around 3,300 metres in the Andes, and some tuberous species lie dormant for years before sprouting.
In the kitchen the flowers taste peppery and brighten salads. They carry about 130 milligrams of vitamin C per 100 grams, similar to parsley, and up to 45 milligrams of lutein, the most measured in any edible plant. Unripe seed pods pickled in vinegar stand in for capers. Mashua, an Andean species, is grown for tubers that smell unpleasant raw but not once cooked, yielding 30 tonnes per hectare at 3,000 metres; pre-Inca sites depict it.
The Spanish physician Nicolás Monardes described the plant in 1569, and the English herbalist John Gerard received seeds by 1597. Gardeners also use nasturtiums as companion plants, luring some pests away and repelling others.
Source: Tropaeolum
